Shorter, sharper .UK domain names are now available alongside .CO.UK domains. If you are the owner of a .CO.UK domain, then the .UK equivalent may have been reserved for you.
For the next five years until 10 June 2019, you will have the first option to register the .UK version of your domain name. After that date (or if your .CO.UK domain expires), the .UK version will be available to anyone for registration.